This invention relates generally to sheet material manipulation and, more particularly, to methods for fabricating friction disc rings.
Clutch and brake assemblies typically used in vehicles, e.g., race cars, air plane landing gear, off-road vehicles, and passenger automobiles, normally include a plurality of alternating friction discs and steel-based opposing plates. Such friction discs are typically fabricated by adhering pre-cut circular discs of friction materials onto steel cores, or steel backing plates, that have the same outer diameter as the pre-cut friction material discs.
These friction disc rings are typically fabricated from "papers" composed of randomly oriented fibers, e.g. KEVLAR.RTM. fiber (a poly-para-phenylene terephthalamide fiber commercially available from Dupont, Advanced Fiber Systems, Richmond, Va. 23234), carbon fiber, cellulose fiber, and others, resin binder, recycled materials, and filler, or the disc rings can be made of woven (i.e. nonrandomly oriented) cloth using various fiber materials. The size of these friction disc rings varies from a few inches to a few tens of inches in outer diameter (OD). Due, at least in part, to the fabrication process and raw material cost, carbon-fiber cloth is expensive.
Typical methods of fabricating friction discs suffer from a very low materials utilization rate. That is, there is a high waste of sheet or cloth materials as typically utilized in the field of friction disc fabrication. For example, if 1-ply rings with an inner diameter of 4.175 in. and an outer diameter of 4.98 in. are cut from a rectangular sheet, there will be approximately a 73% waste of material. In the automotive transmission industry, friction paper waste can be as high as about 80%-90%.
Additionally, in wet clutches and brakes, friction discs usually include groove patterns in the surface of the friction materials for the purpose of aiding fluids to flow from an inner diameter side to an outer diameter side of the friction and opposing discs. After bonding friction materials to steel cores, grooving machines are typically used to cut grooves on the surface of the friction discs. The grooving process is an added step, and the groove patterns are often limited to simple geometry.
Accordingly, it would be desirable to provide a method for fabricating a friction disc ring that substantially reduces, or eliminates wasted friction paper or cloth. It also would be desirable if the method for fabricating provided grooves and patterns in the discs without additional fabrication steps.